The present invention relates to an electron gun of ceramic-metal construction and, more particularly, to a method of constructing an electron gun having a novel bimetal transition member which is used in such a gun between a common ceramic member and at least one of the metal gun elements. The novel transition member is substantially free of sharp or rough edges. Consequently, the present electron gun has better electrical stability than prior electron guns of ceramic-metal construction that used prior transition members.
U.S. patent application, Ser. No. 735,261, filed on May 17, 1985 by H. E. McCandless and assigned to the assignee of the present invention, discloses an electron gun having a transition member brazed directly to a major surface of a common ceramic member. The metal gun elements are then welded to the transition member in order to prevent distortion of the gun elements during brazing. This procedure prevents cracking of the ceramic member. The transition member is formed from two layers of dissimilar metal bonded face-to-face to form a bimetal. The first layer is a relatively thick nickel-iron alloy layer and the second layer is a relatively thin layer of copper. The transition member includes an electrode contact portion and a removable frame portion connected to the electrode contact portion by a weakened bridge region. The weakened bridge region is formed by providing a pair of oppositely disposed and substantially aligned notches in the transition member. The notches are formed such that the top notch extends partially through the nickel-iron first layer. The corresponding lower notch extends completely through the copper second layer and into the nickel-iron first layer. The top and bottom notches are spaced apart but aligned to facilitate breaking the frame portion away from the electrode contact portion at the weakened bridge region after the transition member is brazed to the common ceramic member. A sharp, rough edge is produced at the weakened bridge region where the frame portion is broken away. This sharp, rough edge is undesirable because of the possibility of injury to manufacturing personnel assembling the electron gun and also because the irregular edge may promote electrical malfunctions, such as cold emission or arcing in the finished tube. Because of cost considerations, it is impractical to eliminate the sharp, rough edge by chemical or mechanical means. Accordingly, it is desirable to eliminate the irregular edge but without adding additional cost to the electron gun.